From: Ondrej Zajicek (work) <santiago@crfreenet.org>
Date: Sun, 6 Mar 2022 21:57:33 +0000 (+0100)
Subject: Filter: Fix bug in variable shadowing
X-Git-Tag: v2.0.11~38^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1e6acf34bbf2d9c31246c6fc450ac3b0232531e2;p=thirdparty%2Fbird.git

Filter: Fix bug in variable shadowing

When a new variable used the same name as an existing symbol in an outer
scope, then offset number was defined based on a scope of the existing
symbol ($3) instead of a scope of the new symbol (sym_). That can lead
to two variables sharing the same memory slot.
---

diff --git a/filter/config.Y b/filter/config.Y
index 82a072abe..51e7822f2 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -408,7 +408,7 @@ function_argsn:
  | function_argsn type symbol ';' {
      if ($3->scope->slots >= 0xfe) cf_error("Too many declarations, at most 255 allowed");
      $$ = cfg_alloc(sizeof(struct f_arg));
-     $$->arg = cf_define_symbol($3, SYM_VARIABLE | $2, offset, $3->scope->slots++);
+     $$->arg = cf_define_symbol($3, SYM_VARIABLE | $2, offset, sym_->scope->slots++);
      $$->next = $1;
    }
  ;
@@ -417,7 +417,7 @@ function_args:
    '(' ')' { $$ = NULL; }
  | '(' function_argsn type symbol ')' {
      $$ = cfg_alloc(sizeof(struct f_arg));
-     $$->arg = cf_define_symbol($4, SYM_VARIABLE | $3, offset, $4->scope->slots++);
+     $$->arg = cf_define_symbol($4, SYM_VARIABLE | $3, offset, sym_->scope->slots++);
      $$->next = $2;
    }
  ;
@@ -425,7 +425,7 @@ function_args:
 function_vars:
    /* EMPTY */ { $$ = 0; }
  | function_vars type symbol ';' {
-     cf_define_symbol($3, SYM_VARIABLE | $2, offset, $3->scope->slots++);
+     cf_define_symbol($3, SYM_VARIABLE | $2, offset, sym_->scope->slots++);
      $$ = $1 + 1;
    }
  ;